Wrench calibrator and bolt tester



April 11, 1961 Filed Dec. 21, 1955 R. H. SKIDMORE WRENCH CALIBRATOR AND BOLT TESTER 2 Sheets-Sheet 1 INVEN TOR. R/c/m/c/ H JK/dmore A #orn eys A ril 11, 1961 R. H. SKIDMORE 2,973,893

WRENCH CALIBRATOR AND BOLT TESTER Filed Dec. 21, 1955 2 Sheets-Sheet 2 ZZcz INVENTOR. Richard A. J/f/omore WRENCH cALmnATon AND BOLT TESTER Richard H. Siridrnore, Lyndhurst, Ohio, assignor to John W. Wilhelm, Cleveland, Ohio Filed Dec. 21, 1955, Ser. No. 554,561

9 Claims. (Cl. 73-1) This invention relates to wrench calibrators and more particularly to portable wrench calibrators and bolt testers.

An object of the present invention is to provide a device by which wrenches may be quickly calibrated for the purpose of accurately tightening bolts to the required tension without overstressing or stripping the threads of the bolts. l

Another object of the present invention is to provide a wrench calibrator which is extremely accurate, and one which reduces error due to cooking, friction and misalignment.

Still another object of the present invention is to provide a relatively light wrench calibrator which is completely self-contained and may be conveniently transported fon use to the scene of construction or Wherever there are wrenches to be calibrated.

This invention may be used for testing the ultimate strength and elastic limit of bolts. it may be used to check defective impact wrenches before and after repan's. l

Another object of the present invention is to provide a wrench calibrator and bolt tester characterized by its structural simplicity, the ease of assembly of its parts, its strongand sturdy nature and its low manufacturing cost. Other features of this invention reside in the arrangement and design of the parts for carrying out their appropriate functions.

Eurther objects of the present invention and certain practical advantages will be referred to in for will be evident from the following description of two embodiments of the invention, as illustrated in the accompanying drawings, in which:

Fig. 1 is a top plan View of my novel wrench calibrator as used in connection with an automatic air impact wrench.

Fig. 2 is an enlarged front elevational view of the calibrator taken along the plane of line 2-2 of Fig. 1.

Fig. 3 is a horizontal cross sectional view taken along the plane of line 3--3 of Fig. 2.

. Fig. 4 is a fragmentary sectional view taken along the plane of line 4- 3 of Fig. 2 and showing the connection between the indicator gauge and the wrench calibrator.

Fig. 5 is an enlarged perspective view of a bushing used, to retain the head of a bolt to be tested, within the wrench calibrator device.

Fig. 6 is a horizontal cross sectional view similar to Fig. 3 but showing a modified form of the present invention. l l

Before describing in detailthe herein disclosed embodiments of the invention, it is to be understood that the present invention is not limited to the structural details or the particular arrangement of parts here shown, as devices embodying the present invention may take other forms. t It also is to be understood that the phraseology and terminology herein used are for purposes of description and not of limitation-as the scope of the present invention is denoted by the appended, claims.

Referring now to Fig. 1, I have shown my novel wrench calibrator 10 removably secured to a suitable rates Patent structure member 11, as a support therefor. A conventional air impact wrench 12 is shown positioned in a calibrating position with respect to the wrench calibrator. As seen in Figs. 2 and 3, the wrench calibrator comprises a cylindrical main body portion 13 having a pair of outwardly projecting arms 14 and 15. Each of the arms is provided with a flange portion 14a and 15a respectively which extend a spaced distance from the outer surface of the main arm portions 14 and 15. The space provided by said flange portion is adapted to receive the edge of a suitable supporting member 11 to which the wrench calibrator may be rigidly secured by means of suitable clamp bolts 16 and 17 respectively.

The cylindrical main body portion 13 is provided with a stepped bore which includes an enlarged cylindrical bore 19 extending inwardly from one side of the main body portion and a smaller bore 20 concentric with said first bore and projecting through the other side of the main body portion, as seen in Fig. 3. The stepped bore provides an annular shoulder at its change in diameter which forms a cylinder head 21 for the main body portion 13. A piston member 22 having a large annular head 22a is received for reciprocation within the large bore 19 of the main body portion 13. The piston member 22 is provided with an annular projection which forms a guide portion 22b and is adapted for reciprocation within the small bore 20. A substantially closed space 18 is provided between the working face 220 of the piston member 22 and the annular cylinder head 21.

This space forms a reservoir and is filled with a suitable fluid such as oil which provides a hydraulic cushion for the piston 22. In order to prevent leakage from the hydraulic reservoir, suitable sealing means which take the form of O-rings 24 and 25 are provided between the cylindrical surfaces of bore 19 and piston 22 on the one hand, and between the smaller bore 2 and the guide portion 22b of piston 22. Each of the 0-rings is supported in a suitable groove contained within the side walls of the bores 19 and 20. As seen in Fig. 3, the outer end of the guide portion'ZZ-b terminates short of the outer surface 13a of the main body portion 13.

The piston member 22 is provided with a centrally located stepped bore having a larger bore 27 and a smaller bore 28. An annular shoulder 29 is provided at the change in diameter of said stepped bore for the purpose of supporting a bushing member 30 as seen in Fig. 3. The smaller bore 28 projects through the guide portion 22b of the piston 22 while the larger bore 27 is provided with an outwardly tapered recess 27a Which communicates with the outer surface of the piston 22.

The bushing member 30, as seen in Figs. 3 and 5, is pro vided for the purpose of supporting a suitable bolt during the wrench calibrating operation. As seen in Fig. 5, the bushing member comprises a cylindrical body portion 31 having a diameter of such size as to be snugly received within the smaller bore 28 of the piston 22 and an enlargedannular head portion 32 having a diameter slightly smaller than the larger bore 27. The enlarged annular head portion 32 is provided with an elongated slot or groove 33 having a width great enough to be capable of receiving the polygon head of a bolt and retaining the flats of said bolt head against rotation. The cylindrical body portion 31 of the bushing member 30 is provided with a through bore 34 which communicates with the groove 33. It will be understood that the bushing member 30 is an interchangeable member and each bushing member is designed for a particular size bolt. Thus, if a wrench were being calibrated for use on /1 inch bolts, then a bushing member 30 having a groove 33 and bore 34 of the particular dimensions of a inch bolt would be used. If a Vs inch bolt were used, then another bushing member designed to receive such bolt would be sub 3 stituted in place thereof. It will be understood that the outer dimensions of the interchangeable bushing member 30 remain the same and only the groove 33 and bore 34 are changed to accommodate the particular size bolt being slightly to relieve pressure on the hydraulic fluid contained in space 18.

A removable nut supporting plate 37 is secured over the openingof bore 28 by means of suitable bolts 38. The supporting plate 37 is provided with a through bore 371; which is concentric to the bore 34 of bushing member 30 in an assembled position, as seen in Fig. 3. In the preferred form of the invention, the bore of plate 37 is of the same diameter as the bore 34 of bushing member 30 and therefore the plate 37 should be changed along with bushing 30 to accommodate the particular size bolt being used.

For the purpose of preventing the piston 22 from ro- .tating during the wrench calibrating operation, a suitable dowel pin 39 is provided in the working face 220 of the piston 22 and is adapted to be reciprocably received within a tapped bore 40 provided in the annular cylinder head 21. The bore 40, as seen in Fig. 3, is of such depth as to permit the free end of the dowel pin to move back and forth as the piston 22 reciprocates. Thus, the dowel pin 39 prohibits rotation of the piston within the bore 19 while permitting said piston to reciprocate within said bore. The bushing member 30 is retained against rotation within the piston 22 by means of dowel pin 41 contained in the shoulder 29 and removably received with a suitable bore 42 provided in the undersurface of the enlarged annular head 32 of the bushing member 30. As seen in Fig. 3, the bore 42 is located in the portion of the large annular head at one side of the groove 33.

A gauge 44, for measuring the hydraulic pressure developed in reservoir '18, and calibrated in terms of bolt tension, is secured to the upper surface of the main body portion 13 and communicates with the hydraulic fluid contained in space 18 via suitable passages 45 contained in said main body portion. The gauge is of a standard type and is provided with a threaded stem portion 46 by which it is secured within the main body portion 13 of the wrench calibrator. The gauge is calibrated in terms of bolt tension which is measured in pounds. The dial is also calibrated to show the desired tension for the standard bolts such as 1 inch, Ma inch, and inch. The calibrating figures as indicated on the gauge for these standard bolts are 15% minimum bolt tension. A U-shaped metal guard 47 forms a protective hood around the gauge 44 and is secured by suitable bolts 48 to the outer surface of the main body portion 13.

The operation of the present device should now be apparent to those skilled in this art. first clamped on any convenient column or beam by means of clamp bolts 16 and 17. A selected bolt 51 and nut 52 to which the impact wrench is to be calibrated is then inserted into its associated bushing so that the head of the bolt is retained within the groove 33 of the bushing 30 and the shank of the bolt projects through the bore 34 of bushing 30 and bore 37a of the plate 37 and then outwardly beyond plate 37, as soon in Fig. 3. A hardened'flat washer 54) is then placed over the bolt shank and rests upon the surface of plate 37. Nut 52 is then secured upon the shank of bolt 51 until it engages the outer surface of the washer 50. A suitable socket 12a, as shown in. Figs. 1 and 3, is provided on the'air impact wrench 12 and is inserted over the nut 52. The nut is then tightened upon the bolt by the impact wrench and above that recommended as The calibrator is i piston around 360 degrees.

in the bolt upon its dial, in pounds.

the actual tension in the bolt is read directly on the hydraulic gauge. As previously pointed out, piston 22 and bushing 30 are retained against rotation by means of dowel pins 39 and 41 respectively. Thus, tightening of the nut upon the bolt has the effect of drawing the piston 22 and its associated working face 22c toward the annular cylinder head 21, as viewed in Fig. 3. The piston 22 has a self-centering reciprocable action due to the close fit between annular head 22a and bore 19, and further because of guide portion 22b which closely'fits the small bore 20. An equalizing pressure also exists since the hydraulic fluid covers the working face of the As the hydraulic fluid in space 18 comes under pressure due to the tightening of the nut 52 upon bolt 51, and the resulting pressure exerted by piston 22, such pressure is transmitted through the fluid in passages 45 to the operating mechanism of the hydraulic gauge 44 which in turn registers the tension The air pressure driving the impact wrench is then set, at a desired point where the gauge shows the proper bolt tension, so that the wrench quits driving when this particular tension is reached. Since varying conditions such as length of air hose, temperature and conditions of the wrench may change as the job progresses, it is recommended that periodic rechecking of the impact wrench be made with the calibrator. The fact that the present device is much smaller and of lighter weight than prior devices facilitates its utility and portability.

In Fig. 6 I have shown a modified form of the present invention which is identical to that shownin Figs. 1 and 3 with the exception of the means for holding the bolt head against turning during testing. In Fig. 6, a bushing 60 having a hollow cylindrical body portion and a flat top is inserted within the smaller bore 28 so that the lower surface of the flat top rests on the shoulder 29. A flat, hardened washer 61 is placed upon the top surface of the bushing prior to insertion of the desired bolt 62. Means are then provided for preventing the bolt from rotating during the wrench calibrating operation. Such means take the form of a removable socket 63 which snugly receives the bolt head, and which is removably retained on a lever arm 64 by means of a suitable ball and socket detent 65. The lever arm 64 is hinged at 66 to a bracket 67 secured to the outer surface of the main body portion 13.' The ball and detent member is contained in a projecting arm 68 which is rigidly secured to lever arm 64 and has a sharp angular contour. arm 68 is here shown with a square contour and is adapted to be received in a square opening provided in the socket 63 and together with lever arm 64 prevents rotation of said socket during wrench calibrating operation. It will be understood that the lever arm 64 in no way interferes with the reciprocal movement of piston 22 within cylindrical body portion 13, since hinge 66 readily accommodates each movement. The pressure developed in reservoir 18, when testing the wrench-tightening action on a bolt, is read on a gauge like 44, as in the firstdescribed form. The socket 63 may be quickly and easily removed'from the bolt head by swinging the lever arm and its associated arm 68 upwardly about the .hinge 66.

It is obvious that a defective impact wrench may be tested on this'device, then repaired and rechecked on this device to insure that it is working properly. In such a case, a stainless steel test bolt might be more or less permanently secured in the testing device.

Another ,use of the invention would be to test the tensile strength of bolts either to the elastic limit or to the ultimate strength which may be read on gauge 44. This device will test a bolt under simulated actual conditions.

In view of the foregoing description, taken in conjunction with the accompanying drawings, it is believed that a clear understanding of the construction, operation and The advantages of the device will be quite apparent to those skilled in this art.

What is claimed is: t 7 t 1. A wrench calibrator and-bolt tester comprising a body having a recess therein, a unitary piston having a head snugly fitting in said recess for slight reciprocation therein, sealing means between the periphery of said piston and the walls of said recess, there being normally a chamber provided between said piston and the bottom of said recess to receive and hold a liquid, said piston floating directlyon said liquid, there being concentric openings centrally through said piston and through the bottomof said recess, sealing means preventing leakage of liquid out said recess bottom opening, means for securing a liquid pressure gauge in communication with said chamber, and separable means for holding against turning relative to said body, the head of a bolt passing through said opening.

2'. A wrench calibrator and bolt tester comprising a hollow cylindrical main body portion, said hollow cylindrical body portion being open at one end and closed at the other end, a piston in sealing engagement with the inner walls of said cylindrical body portion and reciprocable within said body portion, fluid means contained between the closed end of said cylindrical body portion and said piston, said piston containing a central bore adapted to receive a bolt therein, means for holding said bolt against turning relative to said body, said closed end of said main body portion containing a bore concentric with said bore in said piston and adapted to permit said bolt to pass therethrough and project outwardly from the closed end of said main body portion, means bridging said body portion bore and engaging said main body portion to support a nut on the free end of said bolt, whereby tightening of said nut will cause said piston to exert pressure upon said fluid means, and gauge means in communication with said fluid means for measuring the pressure exerted thereon.

3. A wrench calibrator and bolt tester comprising a cylindrical body portion, said cylindrical body portion being open at one end and closed at the other end, an enlarged cylindrical bore extending inwardly from the open end of said main body portion, the closed end of said main body portion being provided with a smaller bore concentric with said first named bore, a piston-like member adapted for reciprocation within said main body portion, an extended guide portion on said piston adapted to project into the smaller of said bores, fluid means between said cylindrical body portion and said piston, sealing means between said piston and said bores preventing leakage of said fluid means, said piston provided with a tapered recess terminating in stepped bore, said stepped bore provided with a shoulder at its change in diameter, a removable bushing member adapted to be supported on said shoulder, said bushing member provided with an enlarged annular head and a body portion having a smaller diameter than said head, said enlarged annular head of said bushing member provided with a groove, said bushing member having a bore extending therethrough, means preventing rotation of said piston in said main body portion while permitting axial reciprocation thereof, means preventing rotation between said slotted bushing member and said piston, said slotted bushing adapted to receive a bolt with a shank of said bolt projecting through said bushing and outwardly through said cylindrical body, and with the head of said bolt being retained against rotation in the groove of said bushing head, whereby tightening of a nut upon said bolt causes said piston to exert an equalized pressure upon said fluid means, and gauging means in communication with said fluid means for accurately measuring the pressure exerted thereon.

4. A wrench calibrator and bolt tester comprising a cylindrical main body portion, said cylindrical body portion being open at one end and closed at the other an extended guide portion on said piston adapted to project into the smaller end of said stepped bore, fluid means between said cylindrical body portion and said piston, sealing means between said piston and said stepped bore preventing leakage of said fluid means, said piston pro vided with a stepped bore, said stepped bore providing a shoulder at its change in diameter, said shoulder adapted to support a removable bushing member, said bushing member provided with a body portion having an enlarged annular head, the enlarged annular head of said bushing member provided with a groove, said bushing member having a bore extending therethrough, said closed end of said cylindrical body portion having an opening concentric with the bore in said bushing, means preventing relative rotation between said piston and said main body portion but permitting axial reciprocation therebetween, means preventing rotation between said bushing member and said piston, said bushing adapted to receive a bolt, said bolt projecting through said bushing and outwardly through the opening in the closed end of said cylindrical body portion, the head of said bolt being retained against rotation in the groove of said bushing head, said plate supporting a nut when secured to said bolt, whereby tightening of said nut upon said bolt causes said piston to exert an equalizing pressure upon said fluid means, and gauging means in communication with said fluid means for accurately measuring the pressure exerted thereon.

5. A wrench calibrator and bolt tester comprising a cylindrical body portion, a bore extending inwardly of said cylindrical body portion, a piston adapted for reciprocation with said bore, fluid means between said cylindrical body portion and said piston, sealing means between said piston and said bore to prevent leakage of said fluid means, said piston provided with a through bore, a removable bushing member received in said through bore of said piston, said bushing member provided with a body portion and an enlarged annular head, said enlarged annular head of said bushing member provided with a groove, said bushing member having a bore extending therethrough, said groove having a width greater than said bore, means preventing relative rotation between said piston and said main body portion but permitting axial reciprocation there-between, means preventing rotation between said grooved bushing member and said piston, said bushing member adapted to receive a bolt, said bolt projecting through said bushing and outwardly through said cylindrical body portion, the head of said bolt being retained against rotation in the groove of said bushing, whereby tightening of a nut upon said bolt causes said piston to exert an equalizing pressure upon said fluid means, and gauging means in communication with said fluid means for accurately measuring the pressure exerted thereon.

6. A wrench calibrator and bolt tester comprising a cylindrical body portion, said cylindrical body portion having a bore, a piston in said bo-re and'reciprocable therein, fluid means contained in said bore between said cylindrical body portion and said piston, means sealing said fluid means in said bore, said piston having a through bore concentric with said first named bore, and terminating at the top in an upwardly opening recess of greater diameter than said last named bore, a bushing having a head receivable in said recess and a shank receivable in said last named bore, said shank having a central through opening to receive a bolt, means pre venting rotation of said bolt, said bolt projecting outwardly from said main body portion, means bridging said body portion bore and engaging said main body por tion to support a nut on the free end of said bolt, whereby tightening of said nut on said bolt will cause said piston to exert pressure upon said fluid means, and gauge means in communication with said fluid means for measuring the pressure exerted thereon.

7. A device as set forth in claim 6, wherein said means preventing rotation of said bolt comprises a recess in the head of said bushing.

8. A device as set forth in claim 6 wherein said means preventing rotation of said bolt comprises means carried by said cylindrical body portion and adapted to engage the head of said bolt and prevent rotation thereof.

9. A wrench calibrator and bolt tester comprising a body portion, a bore in said body portion, a single piston in sealing engagement with said bore and reciprocable within said body portion, fiuid means contained between said body portion and said piston, there being concentric openings centrally through said piston and through the bottom of said bore in said body portion, means for holding against turning relative to said body portion, the head of a bolt passing through said concentric openings, whereby tightening a nut to the free end of said bolt will cause said piston to exert pressure upon said fluid means, and gauge means in communication withsaid fluid means for measuring the pressure exerted thereon.

References Cited in the file of this patent UNITED STATES PATENTS 

